Hexbyte Hacker News Computers Oxford Electric Bell

Charged by the two piles, the clapper moves back and forth between the two bells.

The Oxford Electric Bell or Clarendon Dry Pile is an experimentalelectric bell that was set up in 1840 and which has run nearly continuously ever since. It was “one of the first pieces” purchased for a collection of apparatus by clergyman and physicist Robert Walker.[1][2] It is located in a corridor adjacent to the foyer of the Clarendon Laboratory at the University of Oxford, England, and is still ringing, though inaudibly due to being behind two layers of glass.

The experiment consists of two brassbells, each positioned beneath a dry pile (a form of battery), the pair of piles connected in series. The clapper is a metal sphere approximately 4 mm in diameter suspended between the piles, which rings the bells alternately due to electrostatic force. As the clapper touches one bell, it is charged by one pile, and then electrostatically repelled, being attracted to the other bell. On hitting the other bell, the process repeats. The use of electrostatic forces means that while high voltage is required to create motion, only a tiny amount of charge is carried from one bell to the other, which is why the piles have been able to last since the apparatus was set up. Its oscillation frequency is 2 hertz.[3]

The exact composition of the dry piles is unknown, but it is known that they have been coated with molten sulphur for insulation and it is thought that they may be Zamboni piles.[2]

The Oxford Electric Bell does not demonstrate perpetual motion. The bell will eventually stop when the dry piles have distributed their charges equally if the clapper does not wear out first.[5][6] The Bell has produced approximately 10 billion rings since 1840 and holds the Guinness World Record as “the world’s most durable battery [delivering] ceaseless tintinnabulation“.[2]